_牛津上海版八年级上册be able to与ought to讲解及练习(有答案)

语法：be able to &ought to

1.be able to的用法

be able to具有现在﹑过去和将来等多种时态。

解析：be able to / can

相同点：当表示“能力”时，差别不大，其后均跟动词原形。一般情况下，两者可互相替换。

不同点：

1)can只有一般现在时(can)和一般过去时(could)两种形式；而be able to有更多的时态形式，如：一般现在时(be able to), 一般过去时(was/were able to), 一般将来时(will be able to) 和现在完成时(has/have been able to)等。

2)be able to 相当于manage to do sth.表示经过一番努力，终于能完成某事；而can无此用法。用于否定的陈述句时两者都有此用法。

3)can能用来表示“请求，许可”，be able to无此用法。

4)can有被动语态，主语为人或物皆可，而be able to只接不定式的主动形式，不接表示被动的不定式，也不可用无生命的名词作主语。

The work is able to be done by him. （误）

He is able to do the work. （正）

2. ought to 的用法

1）表示义务，责任等应当，应该

We ought to obey school rules. 我们应该遵守学校的规则。

2）表示劝告，建议等应当，应该

You don’t look well. You ought to go to see a doctor.

你看起来脸色不好，你应该去看医生。

3）表示猜测，期望应该

It ought to be a fine day tomorrow.明天应该是晴天。

4）

注意：ought to的疑问式是将ought提到句首构成，否定式是ought not/ oughtn’t to, 其反意疑问句有两种形式。

一般疑问句：Ought we to do it at once? 我们要立刻做吗？

肯定回答：Yes, we ought to.是的，我们要。

否定回答：No, we oughtn’t to. 不，我们不要。

反意疑问句：He ought to be here now, shouldn’t / oughtn’t he?

他现在应该在这，难道不是吗？

Practice

I.Choose the best answer. （选择最恰当的答案）

1. I think a student _______ to broaden his mind.

A.ought

B.should

C.must

D.may

2.You _______ to go to school today because it is Saturday today.

A.needn’t

B.needn’t to

C.don’t need to

D.don’t need

3._______ you _______ make a homepage on the Internet soon?

A.Can, be able to

B.Do, able to

C.Were, able to

D.Will, be able to

4.-Must I return the magazine to you right now, Tom?

-No, you ________. You may keep it until next week.

A.mustn’t

B.can’t

C.shouldn’t

D.needn’t

5.The Internet _______ us _______ get more information.

A.enable to

B.enables, for

C.enables, to

D.able, to

【答案】1.A 2.D 3.D 4.D 5.C

II. 选用may, must, can, can’t, should填空：

1. “______ your brother speak English very well, too?” No, he ______.”

2. “______ you play tennis?” “Yes, I ______.”

3. The box is very heavy. Tom ______ move it.

4. “What about seeing a new film this evening?”

“I’m afraid I ______. I ______ finish my English exercises this evening.”

5. This fish won’t keep fresh, we ______ eat it now.

6. You ______ start now, or you’ll be late.

7. Excuse me, sir. ______ I ask you a question, please?

8. I’m not sure about the news. It ______ or ______ not be true.

9. Lily isn’t here. She ______ have gone to the school library, or she ______ have gone to the meeting room, or she ______ have gone home. Who knows?

【答案】1.Can, can’t 2.Can, can 3.can’t 4.can’t, must 5.must 6.must7.Can 8.may, may 9.may, may, may

Homework

I.Choose the best answer. （选择最恰当的答案)]

1.We all agree _______ him.

A.to

B.at

C.with

D.for

2.Tom’s father is worried _______ his health.

A.about

B.at

C.with

D.for

3.She gets angry easily. So she has made _______ friends here.

A.a little

B.little

C.few

D.a few

4.The headmaster often tells us _______ dishonest.

A.be

B.to be

C.not be

D.not to be

5.You don’t look _______. What’s wrong with you?

A.well

B.good

C.nice

D. happily

6.Please help ________ to make a cake, will you?

A.I

B.me

C.you

D.yourself

【答案】1.C 2.A 3.C 4.D 5.A 6.D

plete the following passages with the words or phrases in the box. Each word can only be used once. （将下列单词或词组填入空格，每空限填一词，每词只能填一次）